Simpler way to paste a texture on lots of Plane faces?
You have several options depending on the result you want, you can scale one plane to any size you want, then either the texture scales up with it, or you setup the texture to repeat over the plane.

You can use two array modifiers to duplicate one piece of mesh in two directions. This will duplicate the same piece repeatedly. Then you can apply the modifiers to turn them into a real mesh object, which is an option during export if you only want it that way in unity.

If you want each piece as a separate item in unity, then apply the array modifers, then in edit mode use P->By Loose Parts to break them into multiple objects and &#9096; Ctrl&#9095; Alt&#8679; ShiftC->Origin to Geometry to put the object centres in the right place.

If you have created multiple planes, select them all A and press &#9096; CtrlL->Material to set them to use the same material.

To automate tasks in blender, we can use python v3 which is also used to create addons. The API reference is here as well as an introduction in the manual. You can also find plenty of scripts around this site for examples.

And if you need help with unity, they have their own site